Optical transceivers are used to transmit and receive optical signals for various applications including, without limitation, internet data center, cable TV broadband, and fiber to the home (FTTH) applications. Optical transceivers provide higher speeds and bandwidth over longer distances, for example, as compared to transmission over copper cables. The desire to provide higher' speeds in smaller optical transceiver modules for a lower cost has presented challenges, for example, with respect to thermal management, insertion loss, and manufacturing yield.
Optical transceiver modules generally include one or more transmitter optical subassemblies (TOSAs) for transmitting optical signals. A TOSA generally includes a laser package for housing a laser diode and a lens optically coupling the laser diode to an optical fiber. In at least one type of TOSA, an aspherical lens is used to provide a relatively high coupling efficiency and the aspherical lens has a square perimeter shape to fit within the laser package. These lenses, however, are often more expensive. Moreover, a lower power output may be desired in some applications without having to redesign the TOSA with a different laser. Thus, the higher coupling efficiency of the aspherical, square lenses may provide a power output that is too high and at a cost that is too high. The design and space restrictions within a TOSA also present challenges with respect to using different lenses.